1. I have seen ads that say resveratrol can help us live longer. What exactly is it? Lynn, Internet

Resveratrol is a plant compound found in the skins of red grapes, grape seeds, purple grape juice and red wine. The ads promote the use of supplements and most resveratrol supplements are made from the Japanese knotweed plant.

There is preliminary evidence that it may help for age-related macular degeneration but the evidence is limited and contradictory for extending life as well as improving cholesterol, diabetes, or blood pressure.

The researchers say more long term studies are needed and are currently being done. So until we know more you may want to eat some dark red and purple foods to get the health benefits they offer and hold off on the resveratrol supplements.

2. Are genetically-modified salmon being sold? Does Farmed or wild salmon have more omega-3 fats? More mercury? More PCBs? Frannie, Chicopee

In 2015, the FDA approved genetically modified salmon but it is not being sold in the U.S. yet. The labeling laws need to be finalized.The FDA said they would not require genetically modified salmon to be labeled but do recommend non GMO fish be labeled as such.

At one time farmed salmon had more of the beneficial omega-3 fats because they were fed fish oil. Now the supply of fish oil is tight so farmed fish get more vegetable oil and the omega-3 fats in farmed salmon are cut in half which is similar to wild salmon now.

All salmon is low mercury. The level of PCBs depends on the farm contamination. Farmed salmon has more PCBs than wild. Researchers looked at the PCB to omega-3 ratio in salmon to determine the best salmon to buy. While wild Pacific Salmon is best, farmed salmon from North America and Chile come in a close second.